1. Field of the Invention
This invention relates to power transmission belts and, more particularly, to a power transmission belt having at least one load carrying cord embedded therein. The invention is also directed to a method of manufacturing such a power transmission belt.
2. Background Art
Power transmission belts have long been used on engines in the automotive industry. Commonly, these belts have been made using natural rubber, styrene-butadiene rubber, or chloroprene rubber.
To improve energy conservation, many automobiles are being made with increasingly smaller designs. This has resulted in very compact engine compartments wherein components of the engines are placed in close proximity to each other. As a consequence, the temperature in such compact compartments is generally higher than it was in larger engine compartments in the past. When power transmission belts are operated in this higher temperature environment, rubber layers made from the above-noted compositions tend to cure. This may lead to premature belt cracking.
To avoid this cracking phenomenon, ethylene-α-olefin rubbers have been used in place of chloroprene rubber. Exemplary rubbers are ethylene-propylene rubber (EPR) and ethylene-propylene-diene rubber (EPDM), both of which exhibit excellent thermal resistance.
Ethylene-α-olefin rubber has the drawback that it does not adhere tenaciously to fibers in load carrying members, normally incorporated into such belts. Different approaches have been followed to improve adhesion between the fibers and the ethylene-α-olefin rubber.
As one example, in Japanese Unexamined Patent Publication No. 2000-234277, there is disclosed a method of treating a fiber material with a resorcinol-formaldehyde-latex liquid (resorcinol-formalin-latex liquid) after which a separate treatment liquid is applied. The treatment liquid is prepared by adding a cross linking agent to a halogenated polymer and vulcanizing for adhesion with an ethylene-α-olefin composition.
While the above treatment may adequately address the problem of adhesion, it introduces another problem. These compositions includes halogen, which generates dioxin. This raises environmental concerns.
Thus, heretofore, the industry, in using ethylene-α-olefin rubber in power transmission belts has been faced with the choices of either: a) contending with belts that may fail by reason of inadequate adhesion between the belt rubber and fibers in load carrying members; or b) creating environmental issues by reason of using halogen-containing compositions.